Expansion bolt

ABSTRACT

The invention relates to an expansible anchor ( 10 ) for anchoring in a cylindrical drilled hole ( 40 ). The invention proposes constructing the expansible anchor ( 10 ) with a tubular basic anchor part ( 12 ), on which a hollow conical expansion portion ( 22 ) is formed by means of a forming procedure, on which expansion portion ( 22 ) an expansion sleeve ( 14 ) bent out of sheet metal is mounted. As a result of axial displacement of the expansion sleeve ( 14 ) on the expansion portion ( 22 ), the expansible anchor ( 10 ) becomes anchored in the drilled hole ( 40 ). The expansible anchor ( 10 ) exhibits subsequent expansion behaviour in the event of widening of the drilled hole ( 40 ), for example as a consequence of crack formation.

[0001] The invention relates to an expansible anchor having the featuresof the preamble of claim 1.

[0002] Expansible anchors of that kind are known per se. The knownexpansible anchors have an anchor bolt provided with a screw thread atthe rear end and with an expansion cone at the front end. The anchorbolt together with the expansion cone may be referred to as the basicanchor part. An expansion sleeve, which is usually divided intoexpansion portions by means of longitudinal slits, is mounted on theanchor bolt. The expansion sleeve is expanded as a result of beingpushed up on the expansion cone and, as a result, it anchors theexpansible anchor in a drilled hole. In the known expansible anchors,expansion is brought about by screwing on and tightening a nut on thescrew thread of the anchor bolt. The nut presses against the expansionsleeve directly or—by way of a sleeve mounted on the anchor bolt,between the nut and the expansion sleeve—indirectly and, as a result,pushes the expansion sleeve up on the expansion cone, expanding theexpansion sleeve. In the case of such expansible anchors it isdisadvantageous that they are complicated and consequently expensive tomanufacture. It is further disadvantageous that expansion is broughtabout by screwing on and tightening the nut on the screw thread of theanchor bolt, which is time-consuming and should always be carried outusing a torque wrench.

[0003] So-called hammer-in anchors are also known, which can be expandedby driving an expansion member into an expansion sleeve. An axial holein the expansion sleeve of such expansible anchors becomes narrowerbetween the expansion portions so that the expansion portions can beexpanded by driving in the preferably conical expansion member. Suchexpansible anchors are economical to manufacture and can be expandedsimply and rapidly by hammer blows with the aid of, for example, a punchand anchored in a drilled hole as a result. Such expansible anchors havethe disadvantage, however, that they exhibit no subsequent expansionbehaviour, slackening in the event of widening of the drilled hole, forexample caused by crack formation, and coming loose.

[0004] The invention is based on the problem of so constructing anexpansible anchor of the kind mentioned at the beginning that it iseconomical to manufacture and simple to anchor and exhibits subsequentexpansion behaviour.

[0005] The problem is solved in accordance with the invention by thefeatures of claim 1. In the case of the expansible anchor according tothe invention having the features of claim 1, the basic anchor part hasa through-hole in the longitudinal direction, which is covered over, forexample, by the end wall of the expansion sleeve at the end which is tothe front in the direction of introduction of the expansible anchor intoa drilled hole. The expansion sleeve can be subjected to axial force,for example by means of a punch, through the through-hole in the basicanchor part, and by that means can be pushed up on the expansion portionof the basic anchor part and, as a result, expanded. The through-hole inthe basic anchor part of the expansible anchor according to theinvention accordingly allows expansion by means of hammering andtherefore allows rapid anchoring with little outlay.

[0006] A further advantage of the expansible anchor according to theinvention is its subsequent expansion behaviour. If tension is appliedto the basic anchor part of the expansible anchor according to theinvention and a drilled hole in which the expansible anchor is anchoredwidens, for example as a consequence of crack formation, the tension onthe basic anchor part causes a displacement of the basic anchor part inrelation to the expansion sleeve which pushes the expansion sleevefurther up on the expansion portion of the basic anchor part and, as aresult, expands it further. As a result, the expansible anchor remainsanchored in the drilled hole with an almost unchanged anchoring force.The expansible anchor according to the invention is intended foranchoring in a cylindrical drilled hole. As a result of its subsequentexpansion behaviour, it is suitable for use, in a cylindrical drilledhole, in zones subject to tensile forces. The expansion portion of theexpansible anchor according to the invention is preferably conical; itis, however, not limited to that shape but may have another shape thatwidens out in the direction of introduction.

[0007] In a preferred embodiment of the invention, the basic anchor partis in the form of a sleeve, which allows simple, rapid and economicalmanufacture of the basic anchor part, for example by means of a formingtechnique. The basic anchor part can be, for example, produced fromsheet metal by bending to form a sleeve or shaped from a tube. Othertechniques for working solid material are also possible.

[0008] The expansion portion has, preferably, the shape of a hollow coneand is formed on the sleeve comprising the basic anchor part. In orderto increase stability in the radial direction, the expansion portion is,in an embodiment of the invention, of double-walled construction.

[0009] In order to be able to expand the expansion sleeve with littleradial force, it has, in an embodiment of the invention, one or moreslits extending in the longitudinal direction. The slits do not have toextend in an axially parallel direction; they may, for example, alsoextend at an angle to a line parallel to the axis.

[0010] In a preferred embodiment of the invention, the expansion sleevehas an internal cone. In conjunction with a conical expansion portion ofthe basic anchor part, this embodiment of the invention results inuniform expansion of the expansion sleeve over its axial length and inthe peripheral direction. A high anchoring force is achieved as aresult. For the purpose of matching a cylindrical drilled hole, theexternal surface of the expansion sleeve is, in an embodiment of theinvention, cylindrical.

[0011] In an embodiment of the invention, there is provided an expansionsleeve peg, which engages in the through-hole in the basic anchor part.On the one hand, the peg serves for subjecting the expansion sleeve toaxial force in order to push it up on the expansion portion.Furthermore, the peg guides the expansion sleeve in the basic anchorpart and prevents tilting or skewing of the expansion sleeve, especiallywhen the expansion sleeve is short in the axial direction.

[0012] In an embodiment of the invention, the expansible anchor has astriking pin, which is located in the through-hole of the basic anchorpart, in the region of the expansion portion. The expansion sleeve canbe subjected to axial force by way of the striking pin and, as a result,pushed up on the expansion portion and expanded. The striking pin hasthe advantage that it does not hinder displacement of the expansionsleeve on the expansion portion after expansion and, as a result, doesnot affect the subsequent expansion behaviour of the expansible anchoraccording to the invention. Furthermore, the striking pin stabilises theexpansion portion of the basic anchor portion against radial stressingso that the expansion region does not yield to pressure applied to theexpansion sleeve in an inward radial direction.

[0013] The invention is explained in greater detail hereinafter withreference to exemplary embodiments illustrated in the drawing, in which:

[0014]FIG. 1 is an axial section through an expansible anchor accordingto the invention;

[0015]FIG. 2 shows the expansible anchor of FIG. 1 in the anchoredstate;

[0016]FIG. 3 is an axial section through a second exemplary embodimentof an expansible anchor according to the invention; and

[0017]FIG. 4 is an axial section through a third exemplary embodiment ofan expansible anchor according to the invention.

[0018] The expansible anchor 10 according to the invention and shown inFIG. 1 has a basic anchor part 12 and an expansion sleeve 14. The basicanchor part 12 is produced from a tube and consequently has athrough-hole 16 in the longitudinal direction. The basic anchor part 12is of hollow cylindrical shape, that is to say has a tubular portion 18,over about ⅔ of its length. Connected to the tubular portion 18, by wayof an annular step-shaped narrowing 20, is an expansion portion 22. Theexpansion portion 22 forms a hollow cone, which widens out away from thetubular portion 18. The direction in which the expansion portion 22widens out is the direction of introduction of the expansible anchor 10into a drilled hole; the expansion portion 22 widens out in thedirection of the front end of the expansible anchor 10. At its front,widened-out end, the expansion portion 22 has an external diameter whichcorresponds approximately to the external diameter of the cylindricalportion 18 minus twice the wall thickness of the expansion sleeve 14;the expansion sleeve 14 has approximately the same external diameter asthe cylindrical portion 18 of the basic anchor part 12. The through-hole16 in the basic anchor part 12 also passes through the expansion portion22.

[0019] The annular step-shaped narrowing 20 and the hollow conicalexpansion portion 22 that widens out in the direction of introduction ofthe expansible anchor 10 are made by forming the tube comprising thebasic anchor part 12. For example, the annular step-shaped narrowing 20and the expansion portion 22 are formed on the tubular portion 18 bymeans of flow-forming. The external circumferential surface of thehollow conical expansion portion 22 is provided with a lubricatingcoating that ensures low-friction axial displaceability of the expansionsleeve 14 on the expansion portion 22 and lastingly prevents “seizing”.“Seizing” is understood to mean that the expansion sleeve 14 isdifficult to move, or is immovable, axially on the expansion portion 22of the basic anchor part 12 as a consequence of corrosion phenomena orthe like.

[0020] The cylindrical portion 18 is provided with an internal thread24, which is produced, for example, by means of tube thread rolling. Theinternal thread 24 allows an article being anchored to be fastened tothe expansible anchor 10 according to the invention. The rear end edgeof the basic anchor part 12, remote from the expansion portion 22, isformed to provide a depth-setting collar 26 as a result of forming inthe outwardly radial direction. The wall of the tubular portion 18 isprovided with outwardly projecting protrusions 28 in order to achievejamming of the basic anchor part 12 in a drilled hole.

[0021] The expansion sleeve 14 is produced from a sheet metal piecewhich is bent to form a sleeve, namely the expansion sleeve 14. Theexpansion sleeve 14 has a continuous longitudinal slit 30, which allowsthe expansion sleeve 14 to widen out/expand. The expansion sleeve 14 canbe provided with further, non-continuous longitudinal slits (not shown)in order to make expansion easier. The expansion sleeve 14 has a hollowcylindrical portion 32, by means of which it surrounds the expansionportion 22 of the basic anchor part 12. The hollow cylindrical portion32 of the expansion sleeve 14 is of approximately the same length as theexpansion portion 22 of the basic anchor part 12. At its end face facingthe tubular portion 18 of the basic anchor part 12, the expansion sleeve14 is formed so that it lies against the inner face of its hollowcylindrical portion 32. The inwardly formed portion 34 has a triangularshape in axial cross-section so that the part of the expansion sleeve 14surrounding the expansion portion 22 of the basic anchor part 12 has acylindrical external surface and has a conical inner surfacecomplementary to the hollow cone of the expansion portion 22. Theconical inner surface of the expansion sleeve 22 so lies against theexpansion portion 22 of the basic anchor part 12 that it is axiallydisplaceable. The external diameters of the tubular portion 18 of thebasic anchor part 12 and of the expansion sleeve 14 are approximatelythe same.

[0022] Formed on the hollow cylindrical portion 32 of the expansionsleeve 22 are outwardly projecting barb-shaped claws 36, which areintended to ensure that the expansion sleeve 14 has a good hold in theaxial direction in a drilled hole, preventing it from being pulled out.

[0023] At the front end face, remote from the tubular portion 18 of thebasic anchor part 12, the expansion sleeve 14 is formed in an inwardsdirection, around the front end edge of the hollow conical expansionportion 22, to provide a peg 38. The peg 38 passes through the expansionportion 22 and protrudes a certain distance into the tubular portion 18of the basic anchor portion 12 of the expansible anchor 10 according tothe invention. The peg 38 guides the expansion sleeve 14 in theexpansion portion 22 and prevents skewing of the expansion sleeve 14.

[0024] Anchoring and use of the expansible anchor 10 according to theinvention is illustrated in FIG. 2. For the purpose of anchoring, theexpansible anchor 10 is introduced, with its expansion sleeve 14 to thefront, into a cylindrical hole 40 drilled, for example, in concrete. Thedrilled hole 40 must be deeper than the expansible anchor 10 is long;the drilled hole 40 can also be a through-hole. The expansible anchor 10is introduced into the drilled hole 40 until its depth-setting collar 26comes into contact with the concrete or until it is flush or slightlyrecessed in the drilled hole 40. Then a striking tool (not shown), forexample a punch, is introduced into the hollow cylindrical portion 18 ofthe basic anchor part 12, and the expansion sleeve 14 is subjected toaxial force, for example by hammer blows, by way of its peg 38. Theexpansion sleeve 14 is, as a result, axially displaced on the expansionportion 22 of the basic anchor part 12 and is widened out, that is tosay expanded. The expansion sleeve 14 jams, or wedges, both itself andthe basic anchor part 12 in the drilled hole 40, the expansible anchor10 according to the invention is anchored in the drilled hole 40.Expansion and anchoring of the expansible anchor 10 in the drilled hole40 can also be performed by machine. An article can be fastened to theexpansible anchor 10 anchored in the concrete, for example by means of abolt (not shown) screwed into the internal thread 24.

[0025] If the drilled hole 40 widens, for example as a result of crackformation in the concrete, axial tension acting on the basic anchor part12 causes axial displacement of the basic anchor part 12 relative to theexpansion sleeve 14, which is fixed in an axially immovable position inthe drilled hole 40 by means of its claws 36. The axial displacement ofthe basic anchor part 12 causes further expansion of the expansionsleeve 14, as a result of which the expansible anchor 10 according tothe invention remains anchored in the widened-out drilled hole 40 withan almost unchanged anchoring force. The expansible anchor 10 accordingto the invention accordingly exhibits so-called subsequent expansionbehaviour in the event of widening of a drilled hole.

[0026] In the case of the expansible anchor 10 according to theinvention and shown in FIG. 3, the expansion portion 22 of the basicanchor part 12 is, at its free, front end edge, formed in an inwardsdirection so that it lies against itself, which means that the expansionportion 22 is double-walled. The portion 42 formed in an inwardsdirection has a triangular shape in axial cross-section; within theexpansion portion 22, the through-hole 16 passing through the basicanchor part 12 is cylindrical. As a result of the double-walledconstruction, the expansion portion 22 of the expansible anchor 10 shownin FIG. 3 has greater stability. The peg 38 of the expansion sleeve 14is of shortened form so that it does not protrude into the tubularportion 18 of the basic anchor part 12. For the purpose of anchoring,therefore, a striking tool having an extension that fits into thethrough-hole 16 a should be used. Otherwise, the expansible anchors 10according to the invention and shown in FIGS. 1 and 3 are of likeconstruction and function in the same manner. To that extent, in orderto avoid repetitions, reference should be made, with regard to FIG. 3,to the statements regarding FIGS. 1 and 2. The same reference numeralsare used for the same components.

[0027] In the case of the expansible anchor 10 according to theinvention and shown in FIG. 4, the peg of the expansion sleeve 14 isshortened to a short stump, which engages in the front end of the hollowconical expansion portion 22 of the basic anchor part 12. A striking pin46 is inserted in the expansion portion 22 with a press fit. Acylindrical grooved pin is used as the striking pin 46. In thisembodiment of the invention, it is advantageous that, in the event ofsubsequent expansion of the expansible anchor 10, the striking pin 46does not take part in the relative movement of the expansion sleeve 14in relation to the basic anchor part 12 and, accordingly, does notimpair the subsequent expansion function. Potential “seizing” of thestriking pin 46 in the expansion portion 22 does not hinder subsequentexpansion of the expansible anchor 10. Furthermore, the striking pin 46stabilises the expansion portion 22 against radial compression.Otherwise, the expansible anchors 10 according to the invention shown inFIGS. 3 and 4 are constructed in the same manner and function in thesame manner; to that extent, in order to avoid repetitions, referenceshould be made to the statements regarding FIG. 3.

1. Expansible anchor having a basic anchor part, which expansible anchoris arranged to be introduced into a drilled hole and has an expansionportion which widens out in the direction of introduction of theexpansible anchor, and having an expansion sleeve, which is so mountedon the expansion portion as to be axially displaceable and is arrangedto be expanded as a result of displacement, characterised in that thebasic anchor part (12) has a through-hole (16, 16 a) in the longitudinaldirection; and the expansion sleeve (14) covers over the through-hole(16 a) in the region of the expansion portion (22).
 2. Expansible anchoraccording to claim 1, characterised in that the basic anchor part (12)is in the form of a sleeve.
 3. Expansible anchor according to claim 1,characterised in that the expansion portion (22) is in the form of ahollow cone formed on the sleeve comprising the basic anchor part (12).4. Expansible anchor according to claim 1, characterised in that theexpansion portion (22) is double-walled.
 5. Expansible anchor accordingto claim 1, characterised in that the expansion sleeve (14) has a slit(30) extending in the longitudinal direction.
 6. Expansible anchoraccording to claim 1, characterised in that the expansion sleeve (14)has an internal cone.
 7. Expansible anchor according to claim 1,characterised in that the expansion sleeve (14) has a cylindricalexternal surface.
 8. Expansible anchor according to claim 1,characterised in that the expansion sleeve (14) has a peg (38), whichengages in the through-hole (16, 16 a) in the basic anchor part (12). 9.Expansible anchor according to claim 1, characterised in that theexpansible anchor (10) has a striking pin (46), which is located in theexpansion portion (22) of the basic anchor part (12) and by way of whichthe expansion sleeve (14) can be subjected to axial force.